1. Field of the Invention
This invention relates to the field of video signal processing, and in particular to the creation of 3-D effects via video sample rate conversion.
2. Description of Related Art
High quality video display systems, such as high definition television (HDTV) systems, are becoming increasingly popular, and therefore increasingly cost and feature competitive. To remain competitive, a system must offer more functionality, or be more attractive to a purchaser, or have other features that distinguish the system from other systems. Preferably, these features are provided at substantially the same cost as systems without these features, so that the combination of features and price facilitate an increase in market share, or profits, or both.
One such distinguishing feature among systems is, for example, a xe2x80x9cpicture-in-picturexe2x80x9d (PIP) capability, wherein a second video image can be superimposed upon a primary video image. When initially offered, PIP capable televisions commanded a higher selling price. Competing systems thereafter offered additional PIP features, such as user-controllable sizing and positioning of the PIP image on the display. Following computer interface paradigms, television systems are currently available that offer xe2x80x9cwindowingxe2x80x9d features, wherein different video images can be displayed in different windows on the television display. The video images can be other television program images, a channel selection guide, or communications related to a primary image, such as a window that contains ancillary information about the program being viewed, a detailed view of an item that is advertised for sale, and so on. Televisions that provide these capabilities often provide a higher profit margin than less capable televisions, particularly when the capability is new, because often the additional cost to add the feature is low, but the demand for the feature is high.
In like manner, providers of Internet-based television can be expected to compete for viewers, in order to allow them to command higher advertising prices. If a particular television display system provides a desirable feature, the providers of the Internet service will provide programs that are capable of using the feature, thereby increasing the demand for that provider""s service, as well as an increased demand for display systems that include the feature.
To achieve the aforementioned PIP and windowing video effects, each video image must be scaled to fit the allocated display area for the image. In a digital display system, sample rate converters (SRCs) are used to effect the scaling. A digitally encoded video image comprises an array of samples of the original image; a display screen area comprises an array of pixels. If the number of samples in the horizontal and vertical direction are equal to the number of pixels in the horizontal and vertical direction, no scaling is necessary. Each sample is mapped to each corresponding pixel, and the resultant displayed image corresponds to the original image. If there are half the number of pixels as there are samples, every other sample is mapped to a corresponding pixel. The resultant image corresponds to an image that is sampled at half the sampling rate of the original samples. That is, a change of scale is equivalent to a change of sampling rate, hence the term xe2x80x98sample rate converterxe2x80x99. Non-integer scaling is effected by generating pixel values corresponding to an estimate of the sample value that would have been obtained had the original sampling rate corresponded to this display scale. These generated pixel values are typically obtained by interpolating the value from a set of samples about each pixel location. Conventional display systems include both a vertical sample rate converter and a horizontal sample rate converter to effect the scaling in either or both dimensions.
Computer graphic systems are available that can produce visual effects on a display screen that convey a concept of depth perception, or three dimensional imaging. These graphic systems use complex graphic accelerator devices to achieve this three dimensional effect. The graphics accelerator devices, however, are not directly compatible with conventional video rendering systems, and are not yet able to meet the quality demands of conventional video display systems. The cost of a graphics accelerator device that can be used to produce three-dimensional effects in a video display system can be expected to substantially increase the cost of the display system.
It is an object of this invention to provide additional features for video display systems. It is a further object of this invention to provide a video display system with three-dimensional effects. It is a further object of this invention to provide three-dimensional effects on a video display system without substantially increasing the cost of the system.
These objects and others are achieved by using the two dimensional sample rate conversion capabilities of a video display system to produce three-dimensional effects. Linear and non-linear scaling is applied to a video image to convey a sense of depth. The three dimensional effects are used to increase the visual appeal of existing and new feature sets in display systems. A multi-faceted object representation, such as a representation of a cube or a pyramid, can be used to display different video images on each facet of the representation. By appropriately scaling each image on each facet, an impression of depth is achieved. The images on the different facets can be selected to represent different aspects of a common theme, such as datacast information related to a primary source of information. Channel changing on a television can be presented as a rotation of the multifaceted object. In like manner, other familiar representations, such as a representation of a book can be used, wherein channel changing is presented as a turning of the pages of the book, each television program being presented on a different page. Advanced features, such as program categorization, can be represented as tabs on the book that facilitate the selection of a particular category. In like manner, a rotation of a multifaceted object about one axis may correspond to a change of channel within a select category, whereas a rotation about another axis may correspond to a change of category. Techniques are presented for achieving these three dimensional effects with calculations that are well suited for execution via the sample rate converters of conventional display systems.